This invention relates generally to sputtering substrates and particularly to a mask for shielding the edges of a substrate during sputtering.
The manufacture and use of cermet resistors for microelectronics and integrated circuits are well known in the art as evidenced by U.S. Pat. Nos. 4,010,312 and 4,071,426. Sputtering techniques also are known in the art as evidenced by U.S. Pat. No. 3,860,507.
In one method of making cermet resistors an insulating substrate, such as ceramic, is sputter coated on both sides with a conductive material, such as tungsten. The coated substrate is then cut into strips, commonly called logs in the art, and the edges are ground smooth to remove chips and burrs formed by the cutting process. A resistive material is applied across the edges of the logs and annealed to form a resistance of known value. The logs are then cut transversely across the width to form the individual resistances. The ends of the resistors thus made are the resistive portion and the sputtered material serves as the conductive portion through which electrical connection to the resistive portion can be made. This technique of making microelectronic resistors is disadvantageous because of the cumbersome and expensive grinding and cleaning procedures required after the sputtered substrates are sliced into the logs. Efforts have been made to decrease the complexity of the manufacturing procedure by cutting the substrate into logs prior to the sputtering process. The logs are then individually sputtered on both sides and the resistive material is applied across the edges, in substantially the same manner as before. This technique is disadvantageous because the sputtered material has a tendency to nonuniformily overlap onto the edges of the logs. The nonconductive spacing between the conductive sides then varies and as a result when the resistive material is applied to the edges the high resistance paths vary randomly and the values of the resistors formed from each log vary randomly.
The instant invention overcomes these disadvantages by the provision of a unique sputtering mask which shields the edges of the substrate from the sputtered material, permitting the manufacture of uniform microelectronic resistors while simultaneously eliminating cumbersome and expensive grinding and cleaning procedures.